The invention relates to a manipulator device for the transfer of laser light into an optical fibre and of the type comprising
supporting means for an optical fibre,
means for adjusting the position of the end face of the optical fibre in the axial direction (z-axis) of the fibre corresponding to the optical axis of the manipulator and in relation to a focused laser beam,
an optical system for the focusing of a laser beam arriving substantially axially at an end face of the optical fibre,
means for adjusting the spot of light provided by the focused laser beam on the end face of the fibre in two axial x- and y-directions perpendicular to each other and to said z-axis, and
means for angularly adjusting the axial direction of the fibre in relation to the axial direction of the laser beam incident on the end face of the fibre.
A manipulator device of the above mentioned type is diclosed in U.S. Patent No. 4,542,956.
By passing laser light onto the end face of an optical fibre a series of demands to be satisfied are made with a view to obtain an optimum transferring efficiency,
1. The laser beam arriving from a laser source is to be focused on the fibre end face to a diameter corresponding to the diameter of the fibre core, with a precision within fractions of .mu.m.
2. The position of the focusing point in the
longitudinal direction of the fibre--defined as the z-axis in a rectangular system of co-ordinates--is to be located at the end face of the fibre, with a precision within some few .mu.m.
3. The position of the focusing point in a plane perpendicular to the z-axis, i.e. an x-y-plane must coincide with the centre of the fibrous core, with a precision within fractions of .mu.m.
4. The angle between the end face of the fibre and the laser beam focused thereat--angle defined by its angular components .theta..sub.x and .theta..sub.y --should be of 90.degree., within .mu.rad.
5. The orientation between the polarization direction of the laser light and the polarization axis of the fibre should be within a few .mu.rad.
In the known manipulator some of the above enumerated demands appear to be fulfilled--at any rate items 1 to 4 --by a structure in which a microscope objective coarsely adjustable in the axial z-direction is used for focusing on a holder and in which a separate fibre holder is used for fine z-, x- and y-adjustment of the end face of the fibre in relation to said objective, and in which the angle between the end face of the fibre and the laser beam is adjusted by tilting said two holders in relation to each other.
It is well known that it may be extremely difficult to effect a fine adjustment or minute trimming of various components of an optical system when different adjustment parameters, viz. x, y, z, .theta..sub.x, .theta..sub.y in the present case, affect each other so that a previously adjusted parameter changes as soon as another parameter is being adjusted.
Moreover, the interspace between the objective and the end face of the fibre, i.e. the focusing zone in the prior manipulator is freely accessible so that said known structure does not take additional parameters into account that may influence the passing efficiency, viz. temperature and vibration stability, humidity and dust on the objective and the end face of the fibre, and so on.